Jeep P0442/P0455 - new gas cap

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My Jeep is getting these EVAP codes. The first thing I tried was an OEM gas cap. Now what? The ccdes come back if they are cleared, not immediately, but shortly.
 
Quote:
A code P0442 most likely means one or more of the following has happened:
- A loose or improperly affixed gas cap
- A non-conforming gas cap (i.e. not factory/original brand)
- A small leak/hole in a fuel vapor hose/tube Other small leak in EVAP system
- Faulty vent o-ring seal
- Defective vent valve
- Defective purge valve
- Defective leak detection pump

Read more at: http://www.obd-codes.com/p0442
Copyright OBD-Codes.com


Quote:
A code P0455 most likely means one or more of the following has happened:
- A loose or improperly affixed gas cap
- A non-conforming gas cap (i.e. not factory/original brand)
- Other leak or damaged piece in EVAP system

Read more at: http://www.obd-codes.com/p0455
Copyright OBD-Codes.com
 
P0442 is for a medium evap system leak, P0455 is for a large leak. There are a lot of things that can cause either code to set. The gas cap seal can sometimes be the problem, or it could also be a cracked or split emissions hose or a bad purge valve or emissions pump. Back in 2010 my Dakota threw a P0442 and it turned out to be a bad evap leak detection pump. I also replaced all of the rubber emissions hoses under the hood while I was at it. Then about 3 weeks ago I had the same P0442 code again. Everything under the hood still checked out OK, so I looked under the truck by the gas tank, the hoses at the charcoal canister are known to crack and set emissions codes. Sure enough, I had a small vent hose with a rubber elbow on it from the canister that is connected to a plastic hose going back to the gas tank. I smeared a good coat of black Permatex on the elbow, cleared the code and have not seen it since.

If you do not see any obvious problems like a cracked hose, it might be best to have a shop do an emissions smoke test. The smoke will show the leak much like when you put a flat tire in water and the bubbles show you where the puncture is located.
 
My Jeep trow the P0455 Code this last weekend. It's happen in the past. Check all EVAP lines running from the fuel tank to the engine. I can't remember what year that they moved the evap leak detection pump from the engine compartment to the rear passenger wheel wheel. But that where my 03 is located. I found a cracked Evap line by the pump on mine. I just replaced the section of bad line and no more codes.
 
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